"Beautiful Sydney with such a bright future was taken from us way too soon. My friend’s sister and someone dear to Meadow," Pollack's son, Hunter, tweeted.

Ryan Petty, whose daughter Alaina also died in the school attack, started the Walkup Foundation to raise awareness of mental health issues both to prevent mass shootings and to help those suffering after they occur.

"It’s devastating, it was hard enough to lose the 17 and to think that more people are suffering to the point where they feel like they need to take their own life, it’s heartbreaking," Petty said.

A GoFundMe set up for Aiello's family had already surpassed its $20,000 goal in one day.